Change Of Cold Wave Trajectory Across North China And Its Possible Mechanism From 1990 To 2011

Based on sturface temperature data from 60 stations of North China,NCEP/NCAR CFSR reanalysis data,NCEP/NCAR reanalysis data and NOAA sea-ice concentration data,the interdecadal change of cold wave trajectory across North China and its possible mechanism from 1990 to 2011 are investigated firstly.Then,cold wave trajectories across North China were grouped into 3 types to analyse the features of trajectory.Finally,we discuss the possible effects of AO to cold wave trajectory across North China.The results are as follows:(1)North China cold waves in the 1990s(2000s)are less(more)frequent but stronger(weaker)in recent 55 years.Greenland(Novaya Zemlya)is the mainly source of cold air in 1990s(2000s).Cold wave in 1990s(2000s)invades North China by the west(north)trajectory.The significant decrease of sea-ice around Novaya Zemlya and Buffin Bay in autumn and winter between 1990-2011 corresponds to following circulation differences:stronger(weaker)westerlies around Arctic and lower(higher)geopotential height of Arcticand weaker(stronger)east Asia trough in 1990s(2000s).Above change of circulation leads to the interdecadal variability of North China cold wave from 1990 to 2011.(2)The North China cold wave trajectories between 1990-2011 are grouped into 3 general types:north-west trajectory;west trajectory;north trajectory.North-west and west cold wave are more likely to happen in 1990s,while north cold wave is more likely to happen in 2000s.North-west cold wave originates from west Siberian Plain,there is sea-ice decrease around Novaya Zemlya and sea-ice increase around Greenland in the 30 days before the outbreak.While north-west cold wave breaking out,the wave train of geopotential height anomaly center on 500 hPa transmits by northwest-southeast direction,there is weak temperature decrease around North China.West cold wave originates from Greenland,there is sea-ice increase around Novaya Zemlya to Greenland in the 30 days before the outbreak.While west cold wave breaking out,the wave train of geopotential height anomaly center on 500 hPa transmits by west-east direction,there is weaker temperature decrease around North China than north-west cold wave.North cold wave originates from Novaya Zemlya,there is sea-ice decrease around Novaya Zemlya to Greenland in the 30 days before the outbreak.While north cold wave breaking out,wave train of geopotential height anomaly center on 500 hPa transmits by north-south direction,there is strong temperature decrease around North China.(3)Arctic Oscillation(AO)effects North China cold wave trajectory significantly.Positive(Negative)AO phase corresponds west(north)pattern of North China cold wave,which is more likely to happen in 1990s(2000s).The possible influence approach is as fellow:the increase(decrease)of sea-ice around Novaya Zemlya and Greenland 30 days before outbreak of cold wave causes the decrease(increase)of Arctic temperature and negative(positive)north pole geopotential height anomaly.These anomalies lead to the positive(negative)AO phase and west-east(north-south)wave train pattern of geopotential height anomaly center at high latitude of Eurasia,which make the North China cold wave trajectory west(north).